If it progresses to people fueling from at home compressors off their own NG line then states will more than likely adopt a pay per mile through an on board transmitter like a smart meter.
Very touchy subject for many. And another reason why the feds are NOT backing NG fuel, because its a bitch to collect revenue on.
Why?? Far easier to equip the home compressor with recording and transmitting means.....just like the "smart" controller on my water heater.